1. Field of the Invention
The invention relates to structures, systems, and methods for treatment of an eye. Exemplary embodiments provide ocular inserts used for drug delivery, along with methods for using ocular inserts positioned on or near the anterior segment of the eye. The exemplary inserts may be worn along the front surface of the eye outside the optical zone, and can deliver one or more drugs at a safe, therapeutically-effective level for at least thirty days.
2. Background of the Invention
A variety of ophthalmic and non-ophthalmic conditions necessitate administration of various drugs to the eye. Eye drops and gels can be effective drug delivery vehicles, but can also have significant disadvantages. Specifically, eye drops mix with fluid in the tear film, but may have a residence time of only 2-5 minutes in the tear film. As little as 5% of the drug may be absorbed locally; some or all of the rest being carried from the lacrimal sac into the lacrimal duct and eventually absorbed into the bloodstream. The absorption into the bloodstream can have at least two adverse effects: first, most of the drug is wasted and, second, the presence of the drug in the bloodstream may have harmful side effects on the rest of the body. Gels may adhere more effectively to the eye, but can also blur the patient's vision for prolonged time periods. Both eye drops and gels need to be reapplied frequently for some therapies. Thus, a need remains for an improved drug delivery method to the eye that is neither cleared out of its targeted location, nor needs frequent reapplication.
In light of the disadvantages of eye drops, it is understandable that a variety of alternatives have been proposed. Among the known alternatives to drops include treatments in which structures containing or impregnated with drugs have been placed under the eyelid.
Such solid ocular dosage forms appear to present significant potential advantages over drop-administered drug treatments of the eyes. In particular, eye drug delivery implants might help overcome low patient compliance, the difficult application and frequent misapplication of traditional eye drops and other dosage forms, and limited effective drug absorption presented by eye drops, while potentially facilitating the advantageous application of advances in polymer chemistry and introduction of the concepts of sustained/controlled drug release from other known drug-delivery systems.
Despite the tremendous potential advantages of drug delivery implants, drug application to the front of the eyes remains dominated by eye drops. Factors that may have contributed to the limited acceptance of prior ocular inserts include their lack of comfort, their propensity for displacement or movement around the eye, their excessive incidents of inadvertent expulsion during sleep or rubbing of eyes, their interference with vision, and/or the difficulty in placing and removing the known drug delivery implants.
In light of the above, new drug delivery devices, systems, and methods would be beneficial, particularly for delivering therapeutic compounds to the anterior segment of the eye. It would be particularly advantageous to provide improved ocular inserts so as to gain both physician and user acceptance, with such inserts ideally being easy to insert and remove, providing patient comfort, being non-toxic and not interfering with vision or oxygen penetration, allowing for reproducible release kinetics, and/or being easy to manufacture at a reasonable price.